June, 1917.] ARSENICAL RESIDUES AFTER SPRAYING. 13 



DISCUSSION OF RESULTS. 



In Table No. 3 the results of analyses are first shown as the total 

 amount of arsenious oxid, AS2O3, recovered for the entire number 

 of apples in the lot analyzed. Following this, in the same line, 

 will be found the amount of arsenic per apple, expressed in milli- 

 grams of AS2O3. 



It will be noted that the amounts are computed per apple, 

 rather than at the usual proportion by weight. This is deemed 

 desirable for the following reason : 



The arsenic that any fruit may carry is naturally all on the 

 surface of the fruit. This is quite different from the case of other 

 food substances, such as candy, where the poison may be found 

 permeating the material. With the latter, as with liquids, the 

 amount per unit of weight is the natural index. With apples 

 the amount per fruit may be considered the natural index and is 

 somewhat more useful, as well as more graphic. 



Examining the results of analysis as given in Table No. 3, we 

 find that where fruit was picked carefully, handling it by the 

 stem only in order not to remove poison from the surface of it, 

 the amount of arsenic per apple varied from .08 milhgram to .77 

 milhgram. The latter is from a special lot of 25 apples picked 

 5 days after the tree was sprayed, without intervening rain, and 

 individually chosen because they appeared to exhibit the largest 

 amount of spray material. Reduced to other terms these several 

 lots of apples disclosed residues of such amount that from 3 to 

 25 apples would be required to equal a medicinal dose of arsenic 

 (2 to 5 milhgrams) and from 80 to 700 to equal a so-called dan- 

 gerous dose (60 milhgrams). 



In the case of fruit picked in the ordinary manner the average 

 residues per apple in the several lots varied from .02 milligram to 

 .5 milligram. This is the equivalent of 4 to 100 apples as repre- 

 senting a medicinal dose of arsenic and 120 to 3,000 apples as 

 representing a dangerous dose. 



Where the fruit was handled wjth cotton gloves in the process 

 of picking the residues ranged from .10 milhgram per apple to 

 .21 milligram per apple, or the equivalent of 10 to 20 apples to 

 equal a medicinal dose, or 300 to 600 to equal a dangerous dose. 



Where the fruit was wiped with cotton gloves in the process of 

 picking, the residues ranged from .08 to .18 milhgram per apple, 



